The increasing threat of AIDS has generated a rapid development of methods for preventing the spread of communicable diseases from the inadvertent reuse of needle devices, accidental needle stick injuries suffered by medical and dental practitioners, and ineffective sterilization of reusable devices. To be effective, the devices employed must be simple to manufacture and easy to use. U.S. Pat. No. 5,108,378 discloses a syringe having a rectangular body cross-section which permits the use of a protector case of matching interior cross section. The present application describes the application of many of the features of the above patent to the design of an aspirating syringe of the type in common use by dentists for the administering of local anesthesia and in a hospital environment for the administering of controlled substances. Both of these medications are normally packaged in glass carpules. A sterilized, single use, shieldable device for use with these carpules will extend the benefits of the self-shielded, disposable safety syringe to these applications.
Numerous attempts have been tried to solve the problems noted above with respect to aspirating syringes. Examples of prior art devices are found in the disclosures of the following U.S. patents.
U.S. Pat. No. 2,925,083 discloses a hood for concealing and guarding the needle of a syringe which may be easily retracted when the needle is inside the patient's mouth.
U.S. Pat. No. 3,046,985 discloses a sleeve adapter which conceals the needle and applies pressure to the gum tissue.
U.S. Pat. No. 3,878,846 discloses a dental type syringe with a disposable body and case, and a reusable finger grip and plunger. The case provides a sterile cover for the body and attached needle prior to use. The reusable finger grip allows the distance between the flanges of the finger grip to be adjusted.
U.S. Pat. No. 4,772,272 discloses an attachment for a reusable dental syringe which incorporates a sheath as part of the disposable needle assembly.
U.S. Pat. No. 4,915,701 discloses a reusable shield for attachment to a reusable dental syringe with a needle disconnect arrangement to enable disconnecting the needle with the shield in place.
U.S. Pat. No. 4,957,490 shows an injection device having a system for retracting a needle into the body using rearward motion of a plunger.
U.S. Pat. No. 4,990,141 discloses a disposable syringe for use with a carpule and having an elongated needle mount on the front of the body with a shield over the elongated mount.
U.S. Pat. No. 5,104,386 discloses a design of reusable, dental type syringe having a spring actuated, semicircular shield.
U.S. Pat. No. 5,112,307 discloses a reusable dental syringe with a slidable needle carrier. The needle carrier and needle are retracted into the body section by means of a plunger.
U.S. Pat. No. 5,116,319 discloses a disposable syringe with a system for retracting the needle into the body cavity by means of a plunger.
U.S. Pat. No. 5,163,917 discloses a separate add-on sheath for use with a standard reusable aspirating syringe.